A MICROSTRUCTURAL STUDY OF CREEP IN SHORT-FIBER-REINFORCED ALUMINUM-ALLOYS

The present study investigates creep in two aluminium-based short fibr e reinforced metal matrix composites which differ in magnesium content . Creep in the two MMCs is the result of two interrelated processes. D uring primary creep load is transferred to the fibres. This eventually causes rupture of the fibres and controls tertiary creep. During prim ary creep a work hardened zone forms around the fibres from where stre sses are induced into the fibres. The work hardened zone can be repres ented by a system of dislocation loops. A recovery mechanism is propos ed which involves the movement of dislocation loops to the fibre ends where they shrink. This process contributes to the total creep strain and is dependent on the build up of the interface. Adding magnesium to the aluminium alloy increases the number and size of particles in the fibre/matrix interface. This results in a longer effective recovery p ath and increases creep strength.